Synthesis of sulfur containing ammonium and phosphonium borates

ABSTRACT

The present invention relates to the preparation of sulfur containing ammonium and phosphonium borates KA, wherein K is a compound of formula (I), and A is an anion of formulae (IIa) or (IIb) by bringing into contact ammonium borates with sulfur containing ammonium or phosphonium halides or sulfonates.

The present invention relates to the preparation of sulfur containing ammonium borates.

Sulfur containing additives comprising sulfur containing ammonium and phosphonium cations and various anions including borates and their application in electrolyte compositions for electrochemical cells are described in WO 2013/026854 A1. According to WO 2013/026854 A1 the sulfur containing additives containing a borate anion like bisoxalato borate are prepared via metathesis of an ionic compound containing a sulfur containing ammonium or phosphonium cation and a halide anion with an alkali salt of the borate anion, e.g. lithium bisoxalato borate.

The use of non-substituted tetraalkyl ammonium borate salts in electrolytes in galvanic cells is known from WO 94/27335 A1. WO 94/27335 A1 describes the preparation of the tetraalkyl ammonium borates by reaction of lithium hydroxide or tetraalkylammonium hydroxide with B(OH)₃ and the desired bidente ligand salicylic acid or catechin. WO 94/27335 A1 also discloses the synthesis of the ammonium borates via metathesis of the lithium borate salt with a tetraalkylammonium halide.

Up to now lithium borate is an expensive raw material. It was an object of the present invention to provide a process for preparing sulfur containing ammonium and phosphonium borates which can be used as alternative to the known processes and which does not require the lithium borate salts. The process shall be cost effective, should allow the use of educts which are easy to prepare, and should allow the efficient preparation of sulfur containing ammonium and phosphonium borates.

This object is achieved by process for preparing a compound KA comprising step (b) bringing into contact a compound KA¹ with a compound K¹A in the presence of a solvent or solvent mixture (i),

wherein

K is a cation of formula (I)

-   wherein -   X is N or P; -   R¹, R², and R³ are selected independently from each other from     C₁-C₁₀ alkyl, C₂-C₁₀ alkenyl, C₂-C₁₀ alkynyl, C₆-C₁₂ aryl, and     C₇-C₂₄ aralkyl, which may be substituted by one or more groups     selected from F, cyclopropyl, 1,2-epoxyethyl, and sulfonate, and     wherein one or more CH₂ groups of alkyl, alkenyl, alkynyl and     aralkyl which are not directly bound to the X-atom may be replaced     by O, 1,2-epoxyethylene, cyclopropylene, OSO₂ or SO₂O; -   or wherein R¹ and R² are linked and jointly selected from     —(CH₂)_(m)— alkylene with m=4 or 5 forming together with the central     X-atom a five- or six-membered heterocycle wherein one or more H of     —(CH₂)_(m)— alkylene may be replaced by one or more substituents     selected from F and optionally fluorinated C₁-C₁₀ alkyl, and wherein     one or more CH₂ groups of —(CH₂)_(m)-alkylene may be replaced by O,     S or NR′; -   R′ is selected from H, C₁-C₁₀ alkyl, C₂-C₁₀ alkenyl, C₂-C₁₀ alkynyl,     C₆-C₁₂ aryl, and C₇-C₂₄ aralkyl, which may be substituted by one or     more groups selected from F, cyclopropyl, 1,2-epoxyethyl, and     sulfonate, and wherein one or more CH₂ groups of alkyl, alkenyl,     alkynyl and aralkyl which are not directly bound to the N-atom may     be replaced by O, 1,2-epoxyethylene, cyclopropylene, OSO₂ or SO₂O; -   L is a —(CH₂)_(n)— chain wherein one or more CH₂ groups of the     —(CH₂)_(n)— chain which are not directly bound to the X-atom or the     OSO₂ group may be replaced by O and wherein a C—C single bond     between two adjacent CH₂ groups of the —(CH₂)_(n)-chain may be     replaced by a C—C double bond or a C—C triple bond; -   n is an integer from 1 to 8; -   R⁴ is selected from C₁-C₂₀ alkyl, C₂-C₂₀ alkenyl, C₂-C₂₀ alkynyl,     C₆-C₁₂ aryl, and C₇-C₂₄ aralkyl, which may be substituted by one or     more groups selected from F, cyclopropyl, 1,2-epoxyethyl, and     sulfonate, and wherein one or more CH₂ groups of alkyl, alkenyl,     alkynyl and aralkyl which are not directly bound to the OSO₂ group     may be replaced by O, 1,2-epoxyethylene, cyclopropylene, OSO₂ or     SO₂O; -   A is an anion of formulae (IIa) or (IIb)

-   wherein -   R⁵ and R⁶ independently from each other are selected from F, C₁-C₂₀     alkyl, OC₁-C₂₀ alkyl, and OC(O)C₁-C₂₀ alkyl, wherein alkyl may be     substituted by one or more F;

independently at each occurrence is a bidentate radical derived from a 1,2- or 1,3-diol, from a 1,2- or 1,3-dicarboxylic acid or from a 1,2- or 1,3-hydroxycarboxylic acid by abstracting the two H atoms of pairs of adjacent OH groups in 1,2- or 1,3-position;

-   A¹ is an anion selected from [R⁷—SO₃]⁻, Cl⁻, Br⁻, and I⁻, wherein -   R⁷ is selected from C₁-C₂₀ alkyl, C₂-C₂₀ alkenyl, C₂-C₂₀ alkynyl,     C₆-C₁₂ aryl, and C₇-C₂₄ aralkyl, which may be substituted by one or     more groups selected from F, cyclopropyl, 1,2-epoxyethyl, and     sulfonate, and wherein one or more CH₂ groups of alkyl, alkenyl,     alkynyl and aralkyl which are not directly bound to the SO₃ ⁻ group     may be replaced by O, 1,2-epoxyethylene, cyclopropylene, OSO₂ or     SO₂O; and -   K¹ is a cation selected from [NR⁸R⁹R¹⁰R¹¹]⁺, wherein -   R⁸, R⁹, and R¹⁰ are selected independently from each other from     C₁-C₁₀ alkyl -   or wherein R⁸ and R⁹ are linked and jointly selected from     —(CH₂)_(p)— alkylene with p=4 or 5 forming together with the central     N-atom a five- or six-membered heterocycle wherein one or more H of     —(CH₂)_(p)— alkylene may be replaced by one or more substituents     selected from C₁-C₁₀ alkyl, and wherein one or more CH₂ groups of     —(CH₂)_(p)— alkylene may be replaced by O, N or NR″, -   R¹¹ is selected from H and C₁-C₁₀ alkyl, and -   R¹¹ is selected independently from R⁸, R⁹, and R¹⁰ from H and C₁-C₁₀     alkyl.

The term “C₁-C₂₀ alkyl” as used herein means a straight or branched saturated hydrocarbon group with 1 to 20 carbon atoms having one free valence and includes, e.g., methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, n-pentyl, iso-pentyl, 2,2-dimethylpropyl, n-hexyl, iso-hexyl, 2-ethyl hexyl, n-heptyl, iso-heptyl, n-octyl, iso-octyl, n-nonyl, n-decyl and the like. Preferred are C₁-C₁₀ alkyl groups, more preferred are C₁-C₆ alkyl groups, even more preferred are C₁-C₄ alkyl groups, and most preferred are methyl, ethyl, and 1- and 2-propyl.

The term “C₂-C₂₀ alkenyl” as used herein refers to an unsaturated straight or branched hydrocarbon group with 2 to 20 carbon atoms having one free valence. Unsaturated means that the alkenyl group contains at least one C—C double bond. C₂-C₂₀ alkenyl includes for example ethenyl, 1-propenyl, 2-propenyl, 1-n-butenyl, 2-n-butenyl, iso-butenyl, 1-pentenyl, 1-hexenyl, 1-heptenyl, 1-octenyl, 1-nonenyl, 1-decenyl and the like. Preferred are C₂-C₁₀ alkenyl groups, more preferred are C₂-C₆ alkenyl groups, even more preferred are C₂-C₄ alkenyl groups and in particular preferred are ethenyl and 1-propen-3-yl (allyl).

The term “C₂-C₂₀ alkynyl” as used herein refers to an unsaturated straight or branched hydrocarbon group with 2 to 20 carbon atoms having one free valence, wherein the hydrocarbon group contains at least one C—C triple bond. C₂-C₂₀ alkynyl includes for example ethynyl, 1-propynyl, 2-propynyl, 1-n-butinyl, 2-n-butynyl, iso-butinyl, 1-pentynyl, 1-hexynyl, -heptynyl, 1-octynyl, 1-nonynyl, 1-decynyl and the like. Preferred are C₂-C₁₀ alkynyl, more preferred are C₂-C₆ alkynyl, even more preferred are C₂-C₄ alkynyl, in particular preferred are ethynyl and 1-propyn-3-yl (propargyl).

The term “C₆-C₁₂ aryl” as used herein denotes an aromatic 6- to 12-membered hydrocarbon cycle or condensed cycles having one free valence. Examples of C₆-C₁₂ aryl are phenyl and naphtyl. Preferred is phenyl.

The term “C₇-C₂₄ aralkyl” as used herein denotes an aromatic 6- to 12-membered aromatic hydrocarbon cycle or condensed aromatic cycles substituted by one or more C₁-C₆ alkyl. The C₇-C₂₄ aralkyl group contains in total 7 to 24 C-atoms and has one free valence. The free valence may be located at the aromatic cycle or at a C₁-C₆ alkyl group, i.e. C₇-C₂₄ aralkyl group may be bound via the aromatic part or via the alkyl part of the aralkyl group. Examples of C₇-C₂₄ aralkyl are methylphenyl, 1,2-dimethylphenyl, 1,3-dimethylphenyl, 1,4-dimethylphenyl, ethylphenyl, 2-propylphenyl, and the like.

The term “sulfonate” as used herein means the groups —S(O)₂O—R′″ or —OS(O)₂—R′″ wherein R′″ is selected from C₁-C₁₀ alkyl, preferably from C₁-C₆ alkyl and more preferred from C₁-C₄ alkyl.

The term “cyclopropylene” as used herein means the group derived from cyclopropane molecule having two free valences at two adjacent C-atoms:

the asterisks denote the two free valences.

The term “1,2-epoxyethyl” as used herein means an oxirane cycle having one free valence:

the asterisk denotes the free valence.

The term “1,2-epoxyethylene” as used herein means an oxirane cycle having two free valences at the two adjacent C-atoms:

the asterisks denote the free valences.

The sulfur containing ammonium borates KA are prepared by bringing into contact compounds K¹A with compounds KA¹ in the presence of a solvent or solvent mixture (i). No lithium borate salt has to be used. The ammonium borate salt K¹A is easily obtainable and less expensive than the analogue lithium borate salts.

In the following the invention is described in detail.

K is a sulfur containing cation of formula (I) as defined above.

X is N or P; preferably X is N.

R¹, R², and R³ are selected independently from each other from C₁-C₁₀ alkyl, C₂-C₁₀ alkenyl, C₂-C₁₀ alkynyl, C₆-C₁₂ aryl, and C₇-C₂₄ aralkyl, which may be substituted by one or more groups selected from F, cyclopropyl, 1,2-epoxyethyl, and sulfonate, and wherein one or more CH₂ groups of alkyl, alkenyl, alkynyl and aralkyl which are not directly bound to the X-atom may be replaced by O, 1,2-epoxyethylene, cyclopropylene, OSO₂ or SO₂O;

or R¹ and R² are linked and jointly selected from —(CH₂)_(m)— alkylene with m=4 or 5 forming together with the central X-atom a five- or six-membered heterocycle wherein one or more H of —(CH₂)_(m)— alkylene may be replaced by one or more substituents selected from F and optionally fluorinated C₁-C₁₀ alkyl, and wherein one or more CH₂ groups of —(CH₂)_(m)— alkylene may be replaced by O, S or NR′.

The five- or six-membered heterocycle formed by R¹ and R² and the central X-atom may be selected for example from

wherein Y is CH₂, O, S or NR′ and the asterisks denote the bonds to L and R³, respectively. Examples of five- or six-membered heterocycles formed by R¹ and R² and the central X-atom are pyrrolidine, piperidine, and morpholine.

If R¹ and R² are not linked, R¹ and R² are preferably selected independently from each other from C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl, C₆-C₁₂ aryl, and C₇-C₁₈ aralkyl, and more preferred from C₁-C₄ alkyl, C₂-C₄ alkenyl, C₂-C₄ alkynyl, C₆-C₁₂ aryl, and C₇-C₁₄ aralkyl, and most preferred from C₁-C₄ alkyl, C₂-C₄ alkenyl, C₂-C₄ alkynyl, wherein alkyl, alkenyl, alkynyl, aryl and aralkyl may be substituted one or more groups selected from F, cyclopropyl, 1,2-epoxyethyl and sulfonate, and wherein one or more CH₂ group of alkyl, alkenyl, alkynyl and aralkyl which are not directly bound to the X-atom may be replaced by O, 1,2-epoxyethylene, cyclopropylene, OSO₂ or SO₂O.

If R¹ and R² are linked they are preferably jointly selected from —(CH₂)₄— alkylene forming together with the central X-atom a five-membered heterocycle wherein one or more H of —(CH₂)₄— alkylene may be substituted by one or more substituents selected from F and optionally fluorinated C₁-C₁₀ alkyl, preferably from F and optionally fluorinated C₁-C₄ alkyl, and wherein one or more CH₂ groups of —(CH₂)₄— alkylene may be replaced by O, S or NR′. The preferred five-membered heterocycle formed by R¹ and R² and the central X-atom is pyrrolidine.

R¹ and R² are preferably linked and jointly selected from —(CH₂)_(m)— alkylene with m=4 or 5 forming together with the central X-atom a five- or six-membered heterocycle, wherein one or more H of —(CH₂)_(m)— alkylene may be replaced by one or more substituents selected from F and optionally fluorinated C₁-C₁₀ alkyl, and wherein one or more CH₂ groups of —(CH₂)_(m)— alkylene may be replaced by O, S or NR′, more preferred m is 4.

R³ is selected independently from R¹ and R² from C₁-C₁₀ alkyl, C₂-C₁₀ alkenyl, C₂-C₁₀ alkynyl, C₆-C₁₂ aryl, and C₆-C₂₄ aralkyl, preferably from C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl, C₆-C₁₂ aryl, and C₇-C₁₈ aralkyl, more preferred from C₁-C₆ alkyl, C₂-C₆ alkenyl, and C₂-C₆ alkynyl, wherein alkyl, alkenyl, alkynyl, aryl and aralkyl may substituted one or more groups selected from F, cyclopropyl, 1,2-epoxyethyl, and sulfonate, and wherein one or more CH₂ groups of alkyl, alkenyl, alkynyl and aralkyl which are not directly bound to the X-atom may be replaced by O, 1,2-epoxyethylene, cyclopropylene or SO₃, preferably by O or SO₃. Even more preferred R³ is methyl, ethyl or propyl, most preferred R³ is methyl.

L is a —(CH₂)_(n)— chain wherein one or more CH₂ groups of the —(CH₂)_(n)— chain which are not directly bound to the X-atom or the OSO₂ group may be replaced by O and wherein a C—C single bond between two adjacent CH₂ groups of the —(CH₂)_(n)-chain may be replaced by a C—C double bond or a C—C triple bond.

n is an integer selected from 1, 2, 3, 4, 5, 6, 7, and 8, preferably n is 1, 2, 3 or 4, more preferred n is 2, 3 or 4.

Preferably L is a non-substituted alkylene chain with n being selected as defined above.

R⁴ is selected from C₁-C₂₀ alkyl, C₂-C₂₀ alkenyl, C₂-C₂₀ alkynyl, C₆-C₁₂ aryl, and C₇-C₂₄ aralkyl, preferably R⁴ is selected from C₁-C₁₀ alkyl, C₂-C₁₀ alkenyl, C₂-C₁₀ alkynyl, C₆-C₁₂ aryl, and C₇-C₂₄ aralkyl, and more preferred C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl, C₆-C₁₂ aryl, and C₇-C₂₄ aralkyl, which may be substituted by one or more groups selected from F, cyclopropyl, 1,2-epoxyethyl, and sulfonate, and wherein one or more CH₂ groups of alkyl, alkenyl, alkynyl and aralkyl which are not directly bound to the OSO₂ group may be replaced by O, 1,2-epoxyethylene, cyclopropylene, OSO₂ or SO₂O; in particular preferred R⁴ is selected from methyl, ethyl, propyl, ethenyl, 1-propen-3-yl ethynyl and 1-propyn-3-yl.

A is a borate anion of formula (IIa) or (lib) as defined above.

R⁵ and R⁶ are selected independently from each other from F, C₁-C₂₀ alkyl, OC₁-C₂₀ alkyl, and OC(O)C₁-C₂₀ alkyl, wherein alkyl may be substituted by one or more F; preferably R⁵ and R⁶ are selected independently from each other from F, C₁-C₆ alkyl, OC₁-C₆ alkyl, and OC(O)C₁-C₆ alkyl, wherein alkyl may be substituted by one or more F, more preferred R⁵ and R⁶ are selected independently from each other from F, C₁-C₄ alkyl, OC₁-C₄ alkyl, and OC(O)C₁-C₄ alkyl, wherein alkyl may be substituted by one or more F, and most preferred R⁵ and R⁶ are F.

is independently at each occurrence a bidentate radical derived from a 1,2- or 1,3-diol, from a 1,2- or 1,3-dicarboxylic acid or from a 1,2- or 1,3-hydroxycarboxylic acid by abstracting the two H atoms of pairs of adjacent OH groups in 1,2- or 1,3-position.

Suited 1,2- and 1,3-diols from which the bidentate radical is derived may be aliphatic or aromatic and are optionally substituted by one or more F and/or by at least one straight or branched non-fluorinated, partly fluorinated or fully fluorinated C₁-C₄ alkyl group. They may be selected, e.g., from 1,2-dihydroxybenzene, propane-1,2-diol, butane-1,2-diol, propane-1,3-diol, butan-1,3-diol, cyclohexyl-trans-1,2-diol and naphthalene-2,3-diol which are optionally are substituted by one or more F and/or by at least one straight or branched non-fluorinated, partly fluorinated or fully fluorinated C₁-C₄ alkyl group. An example for such 1,2- or 1,3-diole is 1,1,2,2-tetra(trifluoromethyl)-1,2-ethane diol.

“Fully fluorinated C₁-C₄ alkyl group” means, that all H-atoms of the alkyl group are substituted by F.

Suited 1,2- or 1,3-dicarboxlic acids from which the bidentate radical is derived may be aliphatic or aromatic, for example oxalic acid, malonic acid (propane-1,3-dicarboxylic acid), phthalic acid or isophthalic acid, preferred is oxalic acid. The 1,2- or 1,3-dicarboxlic acid are optionally substituted by one or more F and/or by at least one straight or branched non-fluorinated, partly fluorinated or fully fluorinated C₁-C₄ alkyl group.

Suited 1,2- or 1,3-hydroxycarboxylic acids from which the bidentate radical is derived may be aliphatic or aromatic and are optionally substituted by one or more F and/or by at least one straight or branched non-fluorinated, partly fluorinated or fully fluorinated C₁-C₄ alkyl group. Examples of such 1,2- or 1,3-hydroxycarboxylic acids are salicylic acid, tetrahydro salicylic acid, malic acid, and 2-hydroxy acetic acid, which are optionally substituted by one or more F and/or by at least one straight or branched non-fluorinated, partly fluorinated or fully fluorinated C₁-C₄ alkyl group. An example for such 1,2- or 1,3-hydroxycarboxylic acids is 2,2-bis(trifluoromethyl)-2-hydroxy-acetic acid.

Examples of borate anions are bis-1,2-benzenediolato borate, bissalicylato borate, difluoro oxalato borate, and bisoxalato borate. Preferably A is selected from difluoro oxalato borate and bisoxalato borate.

Compounds of formula KA are described in detail in the not yet published European patent application EP 14163429.5.

K¹ is a cation selected from [NR⁸R⁹R¹⁰R¹¹]⁺ wherein R⁸, R⁹, and R¹⁰ are selected independently from each other from C₁-C₁₀ alkyl, preferably C₁-C₆ alkyl and most preferred from C₁-C₄ alkyl, or wherein R⁸ and R⁹ are linked and jointly selected from —(CH₂)_(p)— alkylene with p=4 or 5, preferably p=4, forming together with the central N-atom a five- or six-membered heterocycle wherein one or more H of —(CH₂)_(p)— alkylene may be replaced by one or more substituents selected from C₁-C₁₀ alkyl, preferably C₁-C₆ alkyl and most preferred from C₁-C₄ alkyl, and wherein one or more CH₂ groups of —(CH₂)_(p)— alkylene may be replaced by O, N or NR″, and R″ is selected from H and C₁-C₁₀ alkyl, preferably from H and C₁-C₆ alkyl, and most preferred from H and C₁-C₄ alkyl, and R¹¹ is selected independently from R⁸, R⁹, and R¹⁰ from H and C₁-C₁₀ alkyl, preferably R¹¹ is selected from H and C₁-C₆ alkyl, more preferred from H and C₁-C₄ alkyl, most preferred R¹¹ is H.

Preferably R⁸, R⁹, and R¹⁰ are same and selected from C₁-C₄ alkyl or R⁸ and R⁹ are linked and jointly selected from —(CH₂)₄— alkylene forming together with the central N-atom a five-membered saturated or aromatic heterocycle wherein one or more H of —(CH₂)₄— alkylene may be replaced by one or more substituents selected from C₁-C₄ alkyl, and wherein one or more CH₂ groups of —(CH₂)₄— alkylene may be replaced by O, N or NR″ with R″ is selected from C₁-C₄ alkyl and R¹⁰ is selected from C₁- to C₄ alkyl, and R¹¹ is selected independently from R⁸, R⁹, and R¹⁰ from C₁-C₄ alkyl and H, preferably R¹¹ is H.

In a preferred embodiment R¹¹ is H and K¹ is a cation selected from [HNR⁸R⁹R¹⁰]⁺ wherein R⁸, R⁹, and R¹⁰ are selected independently from each other as defined above.

The anion A¹ is preferably selected from [R⁷—SO₃]⁻ more preferred from [R⁷—SO₃]⁻ wherein R⁷ is selected from C₁-C₁₀ alkyl, C₂-C₁₀ alkenyl, C₂-C₁₀ alkynyl, C₆-C₁₂ aryl, and C₇-C₂₄ aralkyl, and more preferred from C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl, C₆-C₁₂ aryl, and C₇-C₂₄ aralkyl, which may be substituted by one or more groups selected from F, cyclopropyl, 1,2-epoxyethyl, and sulfonate, and wherein one or more CH₂ groups of alkyl, alkenyl, alkynyl and aralkyl which are not directly bound to the OSO₂ group may be replaced by O, 1,2-epoxyethylene, cyclopropylene, OSO₂ or SO₂O; in particular preferred R⁷ is selected from methyl, ethyl, propyl, ethenyl, and 1-propyn-3-yl. In case A¹ is [R⁷—SO₃]⁻ no halide anions are used which have to be removed carefully if compound KA is used in lithium ion batteries, since halides have a detrimental effect on the life time of lithium ion batteries.

Especially preferred A¹ is an anion selected from [R⁷—SO₃]⁻ and R⁴ and R⁷ are same. Compounds KA¹ wherein R⁴ and R⁷ are same are easily prepared in one step as described below. The use of symmetrical educts for the preparation of KA¹ which are substituted twice by the same substituent SOR⁴ in comparison to educts which are unsymmetrically substituted is simpler. The synthesis of KA¹ from educts substituted by halogen and SOR⁴ is more complicated and expensive.

In a preferred embodiment of the preparation process

K is a cation of formula (I), wherein X is N, R¹ and R² form together with the central X-atom a five-membered heterocycle, R³ and R⁴ are selected from C₁ to C₆ alkyl, and L is a —(CH₂)_(n)-chain with n=1, 2, 3 or 4;

A is an anion selected from bis(oxalato) borate and difluoro oxalato borate, preferred is bis(oxalato) borate;

K¹ is a cation selected from [NR⁸R⁹R¹⁰R¹¹]⁺ wherein R⁸, R⁹, and R¹⁰ are selected independently from each other from C₁-C₆ alkyl or wherein R⁸ and R⁹ are linked and jointly selected from —(CH₂)₄— alkylene forming together with the central N-atom a five-membered heterocycle and R¹¹ is selected independently from R⁸, R⁹, and R¹⁰ from H and C₁-C₆ alkyl, preferably R¹¹ is H; and A¹ is an anion selected from [R⁷—SO₃]⁻ wherein R⁷ is selected from C₁-C₆ alkyl.

K¹A and KA¹ are brought into contact in the presence of a solvent or solvent mixture (i). Any solvent or solvent mixture suitable may be used, e.g. the solvent or solvent mixture (i) may be selected from C₁ to C₆ alcohols, di-C₁ to C₆ alkylethers, C₁ to C₄ carboxylic acid C₁ to C₄ alkylesters, di-C₁ to C₄ alkyl carbonates, acetonitrile and C₁ to C₄ ketones and mixtures thereof.

The term “C₁ to C₆ alcohol” means an alcohol containing 1 to 6 C-atoms and at least one alcoholic OH-group. Examples of C₁ to C₆ alcohols include methanol, ethanol, n-propanol, i-propanol and the like, preferred is methanol.

Examples of di-C₁-C₆-alkylethers are dimethylether, ethylmethylether, diethylether, diisopropylether, di-n-butylether, and methyl-tert-butylether, preferred is methyl-tert-butylether.

The term “C₁ to C₄ carboxylic acid C₁ to C₄ alkylester” means an ester of a carboxylic acid containing 1 to 4 C-atoms and an alcohol containing 1 to 4 C-atoms. Examples of C₁ to C₄ carboxylic acid C₁ to C₄ alkylester are methyl formiate, ethyl formiate, methyl acetate, ethyl acetate, methyl proprionate and methyl butanoate. Preferred are methyl acetate and ethyl acetate.

Di-C₁ to C₄ alkyl carbonates are acyclic organic carbonates, wherein each C₁ to C₄ alkyl group is selected independently from each other. Examples are diethyl carbonate (DEC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), and methylpropyl carbonate. Preferred are diethyl carbonate (DEC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC). Examples of C₁ to C₄ ketones are acetone and ethylmethylketone. Preferred is acetone.

Compound KA¹ is brought into contact with compound K¹A in the presence of a solvent or solvent mixture (i). This step is also referred to as step (b). Step (b) may e.g. be conducted by preparing a mixture of KA¹ or K¹A with the solvent or solvent mixture (i) and adding K¹A or KA¹, respectively, or preparing a mixture of KA¹ and K¹A and the solvent or solvent mixture (i) or by preparing a mixture of KA¹ with a first solvent or solvent mixture (i) and a mixture of K¹A with a second solvent or solvent mixture (i) and bringing the two mixture into contact with each other, e.g. by adding one solution to the other and mixing, stirring and/or shaking. The first solvent or solvent mixture (i) and second solvent or solvent mixture (i) may be same or different.

A mixture of compound KA¹, K¹A or both with the solvent or solvent mixture (i) is preferably a solution of KA¹, K¹A or both in the solvent or solvent mixture (i). A solution of a compound means herein that the compound is soluble in the solvent or solvent mixture at a concentration of at least 1 g/L at 25° C.

Preferably in step (b) a solution of KA¹ in a first solvent or solvent mixture (i) is brought into contact with a solution of K¹A in a second solvent or solvent mixture (i). The first solvent or solvent mixture (i) and second solvent or solvent mixture (i) may be same or different. According to one embodiment, the first solvent or solvent mixture (i) and second solvent or solvent mixture (i) may be same.

During or after step (b) compounds KA or K¹A¹ are separated from each other. One possibility is to precipitate one of the two compounds KA or K¹A¹ while the other compound is maintained as solution in the solvent or solvent mixture (i). Afterwards the compound in precipitate form is separated from the solution of the other compound in the solvent or solvent mixture (i). Preferably compound KA is precipitated during or after step (b) and is separated from the mixture containing the solvent or solvent mixture (i) and K¹A¹ in dissolved form.

Precipitation of one of the two compounds KA or K¹A¹ may be induced for example by choosing the solvent or solvent mixture (i) present in the mixture obtained in step (b) such that one of the compounds KA or K¹A¹ is not or only partially soluble in the solvent or solvent mixture (i) present in the mixture obtained in step (b), preferably the solubility of either KA or K¹A¹ in the solvent or solvent mixture (i) present in the mixture obtained in step (b) is at maximum 10 mg/L at 25° C. It is also possible to add a non-solvent for one of KA or K¹A¹ to the mixture obtained in step (b) to amend the solubility of KA or K¹A¹, respectively. Another possibility is to decrease the solubility of one of KA or K¹A¹ in the mixture obtained in step (b) by lowering the temperature of the mixture obtained in step (b).

Preferably compound KA is precipitated in the mixture obtained in step (b) during or after step (b), more preferred compound KA is precipitated during step (b) by choosing the solvent or solvent mixture (i) such that KA is not or only partially soluble in the solvent or solvent mixture (i) present in the mixture obtained in step (b) or compound KA is precipitated after step (b) by decreasing the solubility of KA in the mixture obtained in step (b) by decreasing the temperature of the mixture obtained in step (b).

For illustration purposes the different possible ways of precipitating selectively KA or K¹A¹ during after step (b) by adjusting the solvents is described in the following in respect of precipitating selectively KA. One alternative comprises using a first solvent (i) in which K¹A and KA are soluble, using a second solvent (i) for KA¹ which is a solvent for KA¹ but a non-solvent for KA and choosing the ratio of the first solvent (i) to the second solvent (i) such that the resulting mixture of solvents (i) in step (b) constitutes a non-solvent for KA but a solvent for K¹A¹, i.e. KA is not or only partially soluble in the resulting mixture of solvents or is altered into a non-solvent for KA by decreasing the temperature of the mixture obtained in step (b) whereas K¹A¹ stays in the dissolved form. Instead of the first or second solvent (i) a solvent mixture (i) may be used, respectively.

An example for this process is shown in the experiments. For the preparation of 1-methyl-1-(2-((methylsulfonyl)oxy)ethyl)-pyrrolidinium bis(oxalatoborate) (KA) solutions of 1-methyl-1-(2-((methylsulfonyl)oxy)ethyl)-pyrrolidinium methansulfonate (KA¹) in methanol and triethylammonium bis(oxalatoborate) (K¹A) in methanol are mixed. Methanol is a non-solvent for 1-methyl-1-(2-((methylsulfonyl)oxy)ethyl)-pyrrolidinium bis(oxalatoborate) (KA), but a solvent for 1-methyl-1-(2-((methylsulfonyl)oxy)ethyl)-pyrrolidinium methansulfonate (KA¹), triethylammonium bis(oxalatoborate) (KA¹), and triethylammonium methansulfonate (K¹A¹).

In a preferred embodiment anion A is bis(oxalato) borate. If A is bis(oxalato) borate it is preferred to use a compound K¹A in step (b) which was prepared by reaction of oxalic acid, B(OH)₃ and NR⁸R⁹R¹⁰. In this case compound K¹A is selected from [HNR⁸R⁹R¹⁰]⁺ bis(oxalato) borate. The reaction of oxalic acid, B(OH)₃ and NR⁸R⁹R¹⁰ may be carried out in a solvent or solvent mixture and the water generated is removed by distillation during the reacting to shift the reaction equilibrium to bis(oxalato) borate. The reaction may be carried out in analogy to the preparation of HBOB described in WO 02/068433 A1.

A preferred embodiment of the present process wherein A is bis(oxalato) borate comprises the steps

-   (a2) preparing a compound K¹A by reacting oxalic acid, B(OH)₃ and     NR⁸R⁹R¹⁰; and -   (b) bringing into contact compound K¹A obtained in step (a2) and     compound KA¹ and in the presence of a solvent or solvent mixture     (i).

In another preferred embodiment a compound KA¹ is used in step (b) which was prepared by reaction of R⁴SO₂—O-L-O—SO₂R⁷ with NR¹R²R³. In case R⁴ and R⁷ are same it is preferred to use R⁴SO₂—O-L-O—SO₂R⁷ for the preparation of KA¹ which was prepared by reaction of HO-L-OH with R⁴SO₂C₁.

A preferred embodiment of the present process comprises the steps

-   (a1) preparing a compound KA¹ by reacting R⁴SO₂—O-L-O—SO₂R⁷ with     NR¹R²R³; and -   (b) bringing into contact compound KA¹ obtained in step (a1) and     compound K¹A and in the presence of a solvent or solvent mixture     (i);

A preferred embodiment of the present process wherein R⁴ and R⁷ are same comprises the steps (a0) Preparing a compound R⁴SO₂—O-L-O—SO₂R⁷ by reaction of HO-L-OH with R⁴SO₂Cl;

-   (a1) preparing a compound KA¹ by reacting R⁴SO₂—O-L-O—SO₂R⁷ obtained     in step (a0) with NR¹R²R³; and -   (b) bringing into contact compound KA¹ obtained in step (a1) and     compound K¹A obtained in step (a2) and in the presence of a solvent     or solvent mixture (i).

A further preferred embodiment of the present process wherein A is bis(oxalato) borate comprises the steps

-   (a1) preparing a compound KA¹ by reacting R⁴SO₂—O-L-O—SO₂R⁷ with     NR¹R²R³; -   (a2) preparing a compound K¹A by reacting oxalic acid, B(OH)₃ and     NR⁸R⁹R¹⁰; and -   (b) bringing into contact compound KA¹ obtained in step (a1) and     compound K¹A obtained in step (a2) in the presence of a solvent or     solvent mixture (i).

In an embodiment which is also preferred A is bis(oxalato) borate and R⁴ and R⁷ are same and the process comprises the steps

-   (a0) preparing a compound R⁴SO₂—O-L-O—SO₂R⁷ by reaction of HO-L-OH     with R⁴SO₂C₁; -   (a1) preparing a compound KA¹ by reacting R⁴SO₂—O-L-O—SO₂R⁷ obtained     in step (a0) with NR¹R²R³; -   (a2) preparing a compound K¹A by reacting oxalic acid, B(OH)₃ and     NR⁸R⁹R¹⁰; and -   (b) bringing into contact compound KA¹ obtained in step (a1) and     compound K¹A obtained in step (a2) and in the presence of a solvent     or solvent mixture (i).

The invention is illustrated by the examples which follow, which do not, however, restrict the invention.

I Preparation of 1-methyl-1-(2-((methylsulfonyl)oxy)ethyl)-pyrrolidinium methansulfonate Ia Preparation of 1,2-ethane diol bismethanesulfonate

EXAMPLE 1

A mixture of 40 g ethylene glycol, 163 g triethylamine, 350 g ethyl acetate and 60.5 g methyl acetate was prepared at 25° C. and was cooled to 0° C. 170 g methane sulfonyl chloride was added in a controlled manner to ensure, that the temperature of the mixture did not exceed 25° C. The suspension obtained was stirred for additional 60 min at 25° C. 325 g deionized water was added and the phases were separated. The solvents were removed from the organic phase at 65° C. in vacuum and the obtained raw product was used in the next step.

Isolated yield (i.e. yield of isolated product) was 85%, purity determined by gas chromatography (GC analysis) was 94 wt.-%.

EXAMPLE 2

A mixture of 0.32 kg ethylene glycol, 1.30 kg triethylamine, 3.59 kg ethyl acetate and 0.48 kg methyl acetate was prepared and cooled to −10° C. 1.21 kg methanesulfonyl chloride was added in a controlled manner to ensure, that the temperature of the mixture did not exceed 4° C. The obtained suspension was stirred for additional 15 min. 2.1 kg deionized water was added and the phases were separated. The organic phase was sequentially washed with additional portions of water, before the solvents were removed at 65° C. in vacuum. The raw product was used in the next step, without further purification.

Isolated yield: 92%; purity (GC Analysis): 98.6 wt %

EXAMPLE 3

1,2-ethane diol bismethanesulfonate was prepared according to example 1. The crude material was further purified by crystallization from methyl-tert-butyl-ether and acetone at 55° C. in order to obtain the product as colorless crystalline material.

Isolated yield: 60%; purity (GC Analysis): 98.8 wt %

Ib Preparation of 1-methyl-1-(2-((methylsulfonyl)oxy)ethyl)-pyrrolidinium methansulfonate

EXAMPLE 4

131 g 1,2-ethane diol bismethanesulfonate obtained according to reaction Ia and 360 mL methanol were stirred for 10 min resulting in a clear solution. The solution was heated to 65° C. and 51 g N-methylpyrrolidine was added. The reaction mixture was stirred for 16 h at 65° C. Solvent and volatile compounds were removed by distillation under vacuum at 60° C. Afterwards methanol was added and the solution of 1-methyl-1-(2-((methylsulfonyl)oxy)ethyl)-pyrrolidinium methansulfonate in methanol can be used directly in step IV a.

EXAMPLE 5

1.03 kg 1,2-ethane diol bismethanesulfonate, obtained according to reaction Ia, was dissolved in 2.2 kg methanol and heated to 60° C. 0.42 kg N-methylpyrrolidine was added and stirring was continued for 12-17 h. Crude 1-methyl-1-(2-((methylsulfonyl)oxy)ethyl)-pyrrolidinium methansulfonate in methanol can be used directly in IVa, without further purification.

EXAMPLE 6

256 g 1,2-ethane diol bismethanesulfonate, obtained according to reaction Ia, was dissolved in 700 mL methanol and heated to 40° C. 119 g N-methylpyrrolidine was added and stirring was continued for 48-60 h. Crude 1-methyl-1-(2-((methylsulfonyl)oxy)ethyl)-pyrrolidinium methansulfonate in methanol can be used directly in IVa, without further purification.

EXAMPLE 7

250 g 1,2-ethane diol bismethanesulfonate, obtained according to reaction Ia, was dissolved in 800 mL acetone and 20 mL methanol and heated to 60° C. 119 g N-methylpyrrolidine was added and stirring was continued for 12-17 h. After cooling, the suspension was filtered, the residue sequentially washed with 100 mL acetone and dried in vacuum. 1-methyl-1-(2-((methylsulfonyl)oxy)ethyl)-pyrrolidinium methansulfonate was obtained as off-white powder in 73% yield.

EXAMPLE 8

250 g 1,2-ethane diol bismethanesulfonate, obtained according to reaction Ia, was dissolved in 800 mL acetone and heated to 60° C. 119 g N-methylpyrrolidine was added and stirring was continued for 12-17 h. After cooling, the suspension was filtered, the residue sequentially washed with 100 mL acetone and dried in vacuum. 1-methyl-1-(2-((methylsulfonyl)oxy)ethyl)-pyrrolidinium methansulfonate was obtained as off-white powder in 85% yield.

EXAMPLE 9

254 g 1,2-ethane diol bismethanesulfonate, obtained according to reaction Ia, was dissolved in 570 mL acetonitrile and heated to 90° C. 128 g N-methylpyrrolidine was added and stirring was continued for 3 h. 570 mL acetone were added, before the reaction mixture was cooled to 0° C. and stirred over night. The suspension was filtered, the residue sequentially washed with 500 mL acetone and dried in vacuum. 1-methyl-1-(2-((methylsulfonyl)oxy)ethyl)-pyrrolidinium methansulfonate was obtained as off-white powder in 90% yield.

II Preparation of triethylammonium bis(oxalatoborate)

EXAMPLE 10

179 g oxalic acid dihydrate and 44 g boric acid were mixed with 70 mL methanol and homogenized. 72 g triethylamine was added to this suspension. The reaction mixture was stirred at 120 to 130° C. while volatile components were removed by distillation for about 2 h. The reaction mixture was cooled down to room temperature and vented with nitrogen. Methanol was added and the mixture was stirred for 1 h at room temperature. The solution of triethylammonium bis(oxalatoborate) was used in IVa.

III Preparation of methylimidazolium bis(oxalatoborate)

EXAMPLE 11

14 g oxalic acid dihydrate and 4.8 g boric acid were mixed with 50 mL methanol and homogenized. 6.4 g methylimidazole was added to this suspension. The reaction mixture was stirred at 60° C. while stirring volatile components were removed by distillation und vacuum up to 150 mbar. The reaction mixture was further concentrated under vacuum at 120° C. and was died completely under 0.5 mbar at 135° C. Methylimidazolium bis(oxalatoborate) was obtained as beige solid with a yield of 80.3%.

IV Preparation of 1-methyl-1-(2-((methylsulfonyl)oxy)ethyl)-pyrrolidinium bis(oxalatoborate) IVa Preparation Via triethylammonium bis(oxalatoborate)

EXAMPLE 12

570 g of the methanolic solution of 1-methyl-1-(2-((methylsulfonyl)oxy)ethyl)-pyrrolidinium methansulfonate obtained in Ib were cooled under vigorous stirring to 0° C. and seed crystals of 1-methyl-1-(2-((methylsulfonyl)oxy)ethyl)-pyrrolidinium bis(oxalatoborate) were added. Afterwards 579 g of the methanolic solution of triethylammonium bis(oxalatoborate) obtained in II was added dropwise within 45 min. The mixture was stirred at 0° C. for 1 h before the cooled suspension obtained was filtrated. The filter cake consisting essentially of 1-methyl-1-(2-((methylsulfonyl)oxy)ethyl)-pyrrolidinium bis(oxalatoborate) was rinsed several times with cold methanol and dried in vacuum under small nitrogen flow.

1-methyl-1-(2-((methylsulfonyl)oxy)ethyl)-pyrrolidinium bis(oxalatoborate) was obtained as colorless solid in a yield of 59.3% based on the ethylene glycol used for the preparation of 1,2-ethane diol bismethanesulfonate in step Ia.

IV b Preparation Via methylimidazolium bis(oxalatoborate)

EXAMPLE 13

14.3 g of 1-methyl-1-(2-((methylsulfonyl)oxy)ethyl)-pyrrolidinium methansulfonate prepared as described in I was dissolved in 50 mL methanol under vigorous stirring and cooled down to 0° C. A methanolic solution of 15 g methylimidazolium bis(oxalatoborate) was added within 45 min dropwise. The mixture was stirred for 1 h at 0° C. The suspension obtained was filtrated. The filtercake consisting essentially of 1-methyl-1-(2-((methylsulfonyl)oxy)ethyl)-pyrrolidinium bis(oxalatoborate) was rinsed with cold methanol several times and dried in vacuum under small nitrogen flow. The product was obtained as colorless solid with a yield of 42.1% based on the ethylene glycol used for the preparation of 1,2-ethane diol bismethanesulfonate in step Ia.

V Preparation of 1-methyl-1-(2-((methylsulfonyl)oxy)ethyl)-pyrrolidinium difluoro(oxalatoborate)

EXAMPLE 14

30 g of 1-methyl-1-(2-((methylsulfonyl)oxy)ethyl)-pyrrolidinium methansulfonate was dissolved in 100 mL methanol, charged with seed crystals of 1-methyl-1-(2-((methylsulfonyl)oxy)ethyl)-pyrrolidinium difluoro(oxalatoborate) and cooled in an ice-bath. A solution of 24 g triethylammonium difluoro(oxalatoborate) in acetonitrile was added dropwise, followed by stirring for an additional hour. The suspension was filtered and the residue sequentially washed with portions of cold methanol. 1-methyl-1-(2-((methylsulfonyl)oxy)ethyl)-pyrrolidinium difluoro(oxalatoborate) was obtained as colorless solid in 48% yield.

EXAMPLE 15

30 g of 1-methyl-1-(2-((methylsulfonyl)oxy)ethyl)-pyrrolidinium methansulfonate was dissolved in 100 mL methanol, charged with seed crystals of 1-methyl-1-(2-((methylsulfonyl)oxy)ethyl)-pyrrolidinium difluoro(oxalatoborate) and cooled in an ice-bath. A solution of 24 g triethylammonium difluoro(oxalatoborate) in methanol was added dropwise, followed by stirring for an additional hour. The suspension was filtered and the residue sequentially washed with portions of cold methanol. 1-methyl-1-(2-((methylsulfonyl)oxy)ethyl)-pyrrolidinium difluoro(oxalatoborate) was obtained as colorless solid in 76% yield.

EXAMPLE 16

30 g of 1-methyl-1-(2-((methylsulfonyl)oxy)ethyl)-pyrrolidinium methansulfonate was dissolved in 100 mL methanol, charged with seed crystals of 1-methyl-1-(2-((methylsulfonyl)oxy)ethyl)-pyrrolidinium difluoro(oxalatoborate) and cooled in an ice-bath. A solution of 24 g triethylammonium difluoro(oxalatoborate) in acetone was added dropwise, followed by stirring for an additional hour. The suspension was filtered and the residue sequentially washed with portions of cold methanol. 1-methyl-1-(2-((methylsulfonyl)oxy)ethyl)-pyrrolidinium difluoro(oxalatoborate) was obtained as colorless solid in 64% yield. 

The invention claimed is:
 1. A process for preparing a compound KA, the process comprising a step (b) of contacting a compound KA¹ with a compound K¹A in the presence of a solvent or solvent mixture (i), to obtain the compound KA, wherein: K is a cation of formula (I):

X is N or P; R¹, R², and R³ are selected independently from C₁-C₁₀ alkyl, C₂-C₁₀ alkenyl, C₂-C₁₀ alkynyl, C₆-C₁₂ aryl, and C₇-C₂₄ aralkyl, which may be substituted by one or more groups selected from F, cyclopropyl, 1,2-epoxyethyl, and sulfonate, and wherein one or more CH₂ groups of alkyl, alkenyl, alkynyl and aralkyl which are not directly bound to the X-atom may be replaced by O, 1,2-epoxyethylene, cyclopropylene, OSO₂ or SO₂O, or R¹ and R² are linked and jointly selected from —(CH₂)_(m)— alkylene with m=4 or 5 forming together with the central X-atom a five- or six-membered heterocycle wherein one or more H atoms of —(CH₂)_(m)— alkylene may be replaced by one or more substituents selected from F and optionally fluorinated C₁-C₁₀ alkyl, and wherein one or more CH₂ groups of —(CH₂)_(m)-alkylene may be replaced by O, S or NR′; R′ is selected from H, C₁-C₁₀ alkyl, C₂-C₁₀ alkenyl, C₂-C₁₀ alkynyl, C₆-C₁₂ aryl, and C₇-C₂₄ aralkyl, which may be substituted by one or more groups selected from F, cyclopropyl, 1,2-epoxyethyl, and sulfonate, and wherein one or more CH₂ groups of alkyl, alkenyl, alkynyl and aralkyl which are not directly bound to the N-atom may be replaced by O, 1,2-epoxyethylene, cyclopropylene, OSO₂ or SO₂O; L is a —(CH₂)_(n)— chain wherein one or more CH₂ groups of the —(CH₂)_(n)— chain which are not directly bound to the X-atom or the OSO₂ group may be replaced by O and wherein a C—C single bond between two adjacent CH₂ groups of the —(CH₂)_(n)-chain may be replaced by a C—C double bond or a C—C triple bond; n is an integer from 1 to 8; R⁴ is selected from C₁-C₂₀ alkyl, C₂-C₂₀ alkenyl, C₂-C₂₀ alkynyl, C₆-C₁₂ aryl, and C₇-C₂₄ aralkyl, which may be substituted by one or more groups selected from F, cyclopropyl, 1,2-epoxyethyl, and sulfonate, and wherein one or more CH₂ groups of alkyl, alkenyl, alkynyl and aralkyl which are not directly bound to the OSO₂ group may be replaced by O, 1,2-epoxyethylene, cyclopropylene, OSO₂ or SO₂O; A is an anion of formulae (IIa) or (IIb):

R⁵ and R⁶ are independently selected from F, C₁-C₂₀ alkyl, OC₁-C₂₀ alkyl, and OC(O)C₁-C₂₀ alkyl, wherein alkyl may be substituted by one or more F groups;

independently at each occurrence is a bidentate radical derived from a 1,2- or 1,3-diol, from a 1,2- or 1,3-dicarboxylic acid or from a 1,2- or 1,3-hydroxycarboxylic acid by abstracting the two H atoms of pairs of adjacent OH groups in 1,2- or 1,3-position; A¹ is an anion selected from [R⁷—SO₃]⁻, Cl⁻, Br⁻, and I⁻; R⁷ is selected from C₁-C₂₀ alkyl, C₂-C₂₀ alkenyl, C₂-C₂₀ alkynyl, C₆-C₁₂ aryl, and C₇-C₂₄ aralkyl, which may be substituted by one or more groups selected from F, cyclopropyl, 1,2-epoxyethyl, and sulfonate, and wherein one or more CH₂ groups of alkyl, alkenyl, alkynyl and aralkyl which are not directly bound to the SO₃— group may be replaced by O, 1,2-epoxyethylene, cyclopropylene, OSO₂ or SO₂O; K¹ is a cation selected from [NR⁸R⁹R¹⁰R¹¹]⁺; R⁸, R⁹, and R¹⁰ are independently selected from C₁-C₁₀ alkyl or R⁸ and R⁹ are linked and jointly selected from —(CH₂)_(n)— alkylene with n=4 or 5 forming together with the central N-atom a five- or six-membered heterocycle wherein one or more H atoms of —(CH₂)_(n)— alkylene may be replaced by one or more substituents selected from C₁-C₁₀ alkyl, and wherein one or more CH₂ groups of —(CH₂)_(n)— alkylene may be replaced by O, N or NR″; R″ is selected from H and C₁-C₁₀ alkyl; and R¹¹ is selected from H and C₁-C₁₀ alkyl.
 2. The process according to claim 1, wherein X is N.
 3. The process according to claim 1, wherein R¹ and R² are linked and jointly selected from —(CH₂)_(m)— alkylene with m=4 or 5 forming together with the central X-atom a five- or six-membered heterocycle wherein one or more H atoms of —(CH₂)_(m)— alkylene may be replaced by one or more substituents selected from F and optionally fluorinated C₁-C₁₀ alkyl, and wherein one or more CH₂ groups of —(CH₂)_(m)— alkylene may be replaced by O, S or NR′.
 4. The process according to claim 1, wherein A is selected from bis(oxalato) borate and difluoro oxalato borate.
 5. The process according to claim 1, wherein R⁸, R⁹, and R¹⁰ are independently selected from C₁-C₄ alkyl or R⁸ and R⁹ are linked and jointly selected from —(CH₂)₄— alkylene forming together with the central N-atom a five-membered saturated or aromatic heterocycle wherein one or more H atoms of —(CH₂)₄— alkylene may be replaced by one or more substituents selected from C₁-C₄ alkyl, and wherein one or more CH₂ groups of —(CH₂)₄-alkylene may be replaced by O, N or NR″ wherein R″ is selected from C₁-C₄ alkyl.
 6. The process according to claim 1, wherein A1 is an anion selected from [R⁷—SO₃]⁻ and R⁴ and R⁷ are the same.
 7. The process according to claim 1, wherein the solvent or solvent mixture (i) is selected from C₁ to C₆ alcohols, di-C₁ to C₆ alkylethers, C₁ to C₄ carboxylic acids, C₁ to C₄ alkylesters, di-C₁ to C₄ alkyl carbonates, acetonitrile, and C₁ to C₄ ketones, and mixtures thereof.
 8. The process according to claim 1, wherein in step (b) a solution of KA¹ in a first solvent or solvent mixture (i) is brought into contact with a solution of K¹A in a second solvent or solvent mixture (i).
 9. The process according to claim 8, wherein the first solvent or solvent mixture (i) and the second solvent or solvent mixture (i) are same.
 10. The process according to claim 1, wherein compound KA is precipitated during or after step (b) and is separated from the mixture containing the solvent or solvent mixture (i) and K¹A¹ in dissolved form.
 11. The process according to claim 10, wherein compound KA is precipitated during step (b) by using a solvent or solvent mixture (i) wherein KA is insoluble or partially soluble in the solvent or solvent mixture (i).
 12. The process according to claim 10, wherein the compound KA is precipitated by decreasing the solubility of KA in the mixture obtained in step (b) by decreasing the temperature of the mixture obtained in step (b).
 13. The process according to claim 1, wherein A is bis(oxalato) borate and compound K¹A was prepared by reaction of oxalic acid, B(OH)₃ and NR⁸R⁹R¹⁰.
 14. The process according to claim 1, wherein compound KA¹ was prepared by reaction of R⁴SO₂—O-L-O—SO₂R⁷ with NR¹R²R³.
 15. The process according to claim 14, wherein R⁴ and R⁷ are the same and R⁴SO₂—O-L-O—SO₂R⁷ is prepared by reaction of HO-L-OH with R⁴SO₂C₁.
 16. The process according to claim 1, wherein A is bis(oxalato) borate and the process comprises: (a1) preparing the compound KA¹ by reacting R⁴SO₂—O-L-O—SO₂R⁷ with NR¹R²R³; (a2) preparing the compound K¹A by reacting oxalic acid, B(OH)₃ and NR⁸R⁹R¹⁰; and (b) contacting the compound KA¹ obtained in step (a1) with the compound K¹A obtained in step (a2) in the presence of a solvent or solvent mixture (i). 